TY  - JOUR
A1  - Jahnke, Knud
A1  - Sanchez, Sebastian F.
A1  - Wisotzki, Lutz
A1  - Barden, Marco
A1  - Beckwith, Steven V. W.
A1  - Bell, Eric F.
A1  - Borch, Andrea
A1  - Caldwell, John A. R.
A1  - Häußler, Boris
A1  - Heymans, Catherine
A1  - Jogee, Shardha
A1  - McIntosh, Daniel H.
A1  - Meisenheimer, Klaus
A1  - Peng, Chen Y.
A1  - Rix, Hans-Walter
A1  - Somerville, Rachel S.
A1  - Wolf, C.
T1  - Ultraviolet light from young stars in GEMS quasar host galaxies at 1.8 < z < 2.75
N2  - We have performed Hubble Space Telescope imaging of a sample of 23 high-redshift (1.8<z<2.75) active galactic nuclei (AGNs), drawn from the COMBO-17 survey. The sample contains moderately luminous quasars (M(B)similar to-23). The data are part of the Galaxy Evolution from Morphologies and SEDs imaging survey that provides high-resolution optical images obtained with the Advanced Camera for Surveys in two bands (F606W and F850LP), sampling the rest-frame UV flux of the targets. To deblend the AGN images into nuclear and resolved (host galaxy) components, we use a point-spread function subtraction technique that is strictly conservative with respect to the flux of the host galaxy. We resolve the host galaxies in both filter bands in nine of the 23 AGNs, whereas the remaining 14 objects are considered nondetections, with upper limits of less than 5% of the nuclear flux. However, when we co-add the unresolved AGN images into a single high signal-to-noise ratio composite image, we find again an unambiguously resolved host galaxy. The recovered host galaxies have apparent magnitudes of 23.0<F606W<26.0 and 22.5<F850LP<24.5, with rest-frame UV colors in the range -0.2<(F606W-F850LP)(obs)<2.3. The rest-frame absolute magnitudes at 200 nm are -20.0<M-200 nm<-22.2. The photometric properties of the composite host are consistent with the individual resolved host galaxies. We find that the UV colors of all host galaxies are substantially bluer than expected from an old population of stars with formation redshift z<=5, independent of the assumed metallicities. These UV colors and luminosities range up to the values found for Lyman break galaxies (LBGs) at z=3. Our results suggest either a recent starburst of, e. g., a few percent of the total stellar mass at 100 Myr before observation, with mass fraction and age strongly degenerate, or the possibility that the detected UV emission may be due to young stars forming continuously. For the latter case we estimate star formation rates of typically &SIM;6 M&ODOT; yr(-1) (uncorrected for internal dust attenuation), which again lies in the range of rates implied from the UV flux of LBGs. Our results agree with the recent discovery of enhanced blue stellar light in AGN hosts at lower redshifts
Y1  - 2004
SN  - 0004-637X
ER  - 
TY  - JOUR
A1  - Cassan, A.
A1  - Beaulieu, Jean-Philippe
A1  - Brillant, Stephane
A1  - Coutures, C.
A1  - Dominik, M.
A1  - Donatowicz, J.
A1  - Jorgensen, Uffe Grae
A1  - Kubas, Daniel
A1  - Albrow, Michael D.
A1  - Caldwell, John A. R.
A1  - Fouque, P.
A1  - Greenhill, John
A1  - Hill, K.
A1  - Horne, Keith
A1  - Kane, Stephen R.
A1  - Martin, Ralph
A1  - Menzies, J. W.
A1  - Pollard, K. R.
A1  - Sahu, K. C.
A1  - Vinter, C.
A1  - Wambsganss, Joachim
A1  - Watson, R.
A1  - Williams, A.
A1  - Fendt, Christian
A1  - Hauschildt, P.
A1  - Heinmueller, Janine
A1  - Marquette, Jean-Baptiste
A1  - Thurl, C.
T1  - Probing the atmosphere of the bulge G5III star OGLE-2002-BUL-069 by analysis of microlensed H alpha line
N2  - We discuss high-resolution, time-resolved spectra of the caustic exit of the binary microlensing event OGLE 2002-BLG-069 obtained with UVES on the VLT. The source star is a G5III giant in the Galactic Bulge. During such events, the source star is highly magnified, and a strong differential magnification around the caustic resolves its surface. Using an appropriate model stellar atmosphere generated by the PHOENIX v2.6 code we obtain a model light curve for the caustic exit and compare it with a dense set of photometric observations obtained by the PLANET microlensing follow up network. We further compare predicted variations in the Halpha equivalent width with those measured from our spectra. While the model and observations agree in the gross features, there are discrepancies suggesting shortcomings in the model, particularly for the Halpha line core, where we have detected amplified emission from the stellar chromosphere after the source star's trailing limb exited the caustic. This achievement became possible by the provision of the very efficient OGLE-III Early Warning System, a network of small telescopes capable of nearly-continuous round-the-clock photometric monitoring, on-line data reduction, daily near-real-time modelling in order to predict caustic crossing parameters, and a fast and efficient response of a 8 m class telescope to a "Target-of-Opportunity" observation request
Y1  - 2004
ER  - 
TY  - JOUR
A1  - Sackett, Penny D.
A1  - Albrow, Michael D.
A1  - Beaulieu, Jean-Philippe
A1  - Caldwell, John A. R.
A1  - Coutures, C.
A1  - Dominik, M.
A1  - Greenhill, John
A1  - Hill, K.
A1  - Horne, Keith
A1  - Jorgensen, Uffe Grae
A1  - Kane, Stephen R.
A1  - Kubas, Daniel
A1  - Martin, Ralph
A1  - Menzies, J. W.
A1  - Pollard, K. R.
A1  - Sahu, K. C.
A1  - Wambsganß, Joachim
A1  - Watson, R.
A1  - Williams, A.
T1  - PLANET II : a microlensing and transit search for extrasolar planets
N2  - Due to their extremely small luminosity compared to the stars they orbit, planets outside our own Solar System are extraordinarily difficult to detect directly in optical light. Careful photometric monitoring of distant stars, however, can reveal the presence of exoplanets via the microlensing or eclipsing effects they induce. The international PLANET collaboration is performing such monitoring using a cadre of semi-dedicated telescopes around the world. Their results constrain the number of gas giants orbiting 1-7 AU from the most typical stars in the Galaxy. Upgrades in the program are opening regions of ''exoplanet discovery space'' - toward smaller masses and larger orbital radii - that are inaccessible to the Doppler velocity technique.
Y1  - 2003
UR  - http://arxiv.org/pdf/astro-ph/0211098
ER  - 
TY  - JOUR
A1  - Jiang, G. F.
A1  - DePoy, D. L.
A1  - Gal-Yam, A.
A1  - Gaudi, B. S.
A1  - Gould, A.
A1  - Han, C.
A1  - Lipkin, Y.
A1  - Maoz, D.
A1  - Ofek, E. O.
A1  - Park, B. G.
A1  - Pogge, R. W.
A1  - Udalski, A.
A1  - Kubiak, Marcin
A1  - Szymanski, M. K.
A1  - Szewczyk, O.
A1  - Zerbrun, K.
A1  - Wyrzykowski, L.
A1  - Soszynski, I.
A1  - Pietrzynski, G.
A1  - Albrow, Michael D.
A1  - Beaulieu, Jean-Philippe
A1  - Caldwell, John A. R.
A1  - Cassan, A.
A1  - Coutures, C.
A1  - Dominik, M.
A1  - Donatowicz, J.
A1  - Fouque, P.
A1  - Greenhill, John
A1  - Hill, K.
A1  - Horne, Keith
A1  - Jorgensen, S. F.
A1  - Jorgensen, Uffe Grae
A1  - Kane, Stephen R.
A1  - Kubas, Daniel
A1  - Martin, Ralph
A1  - Menzies, J. W.
A1  - Pollard, R.
A1  - Sahu, K. C.
A1  - Wambsganss, Joachim
A1  - Watson, R.
A1  - Williams, A.
T1  - OGLE-2003-BLG-238 : Microlensing mass estimate of an isolated star
N2  - Microlensing is the only known direct method to measure the masses of stars that lack visible companions. In terms of microlensing observables, the mass is given by M (c(2)/4G)(r) over tilde (E)theta(E) and so requires the measurement of both the angular Einstein radius theta(E) and the projected Einstein radius (r) over tilde (E). Simultaneous measurement of these two parameters is extremely rare. Here we analyze OGLE-2003-BLG-238, a spectacularly bright (I-min 10.3), high-magnification (A(max) 170) microlensing event. Pronounced finite-source effects permit a measurement of theta(E) = 650 muas. Although the timescale of the event is only t(E) 38 days, one can still obtain weak constraints on the microlens parallax: 4.4 AU < <(r)over tilde>(E) < 18 AU at the 1 &sigma; level. Together these two parameter measurements yield a range for the lens mass of 0.36 M-&ODOT; < M < 1.48 M-&ODOT;. As was the case for MACHO- LMC-5, the only other single star (apart from the Sun) whose mass has been determined from its gravitational effects, this estimate is rather crude. It does, however, demonstrate the viability of the technique. We also discuss future prospects for single-lens mass measurements
Y1  - 2004
SN  - 0004-637X
ER  - 
TY  - JOUR
A1  - Barden, Marco
A1  - Rix, Hans-Walter
A1  - Somerville, Rachel S.
A1  - Bell, Eric F.
A1  - Häußler, Boris
A1  - Peng, Chen Y.
A1  - Borch, Andrea
A1  - Beckwith, Steven V. W.
A1  - Caldwell, John A. R.
A1  - Heymans, Catherine
A1  - Jahnke, Knud
A1  - Jogee, Shardha
A1  - McIntosh, Daniel H.
A1  - Meisenheimer, Klaus
A1  - Sanchez, Sebastian F.
A1  - Wisotzki, Lutz
A1  - Wolf, C.
T1  - GEMS : the surface brightness and surface mass density evolution of disk galaxies
N2  - We combine HST imaging from the GEMS ( Galaxy Evolution from Morphologies and SEDs) survey with photometric redshifts from COMBO-17 to explore the evolution of disk-dominated galaxies since z less than or similar to 1.1. The sample is composed of all GEMS galaxies with Sersic indices n < 2.5, derived from fits to the galaxy images. We account fully for selection effects through careful analysis of image simulations; we are limited by the depth of the redshift and HST data to the study of galaxies with M-V less than or similar to -20, or equivalently, log (M/M-circle dot) greater than or similar to 10. We find strong evolution in the magnitude-size scaling relation for galaxies with M-V less than or similar to -20, corresponding to a brightening of similar to 1 mag arcsec(-2) in rest-frame V band by z similar to 1. Yet disks at a given absolute magnitude are bluer and have lower stellar mass-to-light ratios at z similar to 1 than at the present day. As a result, our findings indicate weak or no evolution in the relation between stellar mass and effective disk size for galaxies with log (M/M-circle dot) greater than or similar to 10 over the same time interval. This is strongly inconsistent with the most naive theoretical expectation, in which disk size scales in proportion to the halo virial radius, which would predict that disks are a factor of 2 denser at fixed mass at z similar to 1. The lack of evolution in the stellar mass-size relation is consistent with an "inside-out'' growth of galaxy disks on average (galaxies increasing in size as they grow more massive), although we cannot rule out more complex evolutionary scenarios
Y1  - 2005
ER  - 
TY  - JOUR
A1  - Kubas, Daniel
A1  - Cassan, A.
A1  - Beaulieu, Jean-Philippe
A1  - Coutures, C.
A1  - Dominik, M.
A1  - Albrow, Michael D.
A1  - Brillant, Stephane
A1  - Caldwell, John A. R.
A1  - Dominis, Dijana
A1  - Donatowicz, J.
A1  - Fendt, Christian
A1  - Fouque, P.
A1  - Jorgensen, Uffe Grae
A1  - Greenhill, John
A1  - Hill, K.
A1  - Heinmüller, Janine
A1  - Horne, Keith
A1  - Kane, Stephen R.
A1  - Marquette, Jean-Baptiste
A1  - Martin, Ralph
A1  - Menzies, J. W.
A1  - Pollard, K. R.
A1  - Sahu, K. C.
A1  - Vinter, C.
A1  - Wambsganss, Joachim
A1  - Watson, R.
A1  - Williams, A.
A1  - Thurl, C.
T1  - Full characterization of binary-lens event OGLE-2002-BLG-069 from PLANET observations
N2  - We analyze the photometric data obtained by PLANET and OGLE on the caustic-crossing binary-lens microlensing event OGLE-2002-BLG-069. Thanks to the excellent photometric and spectroscopic coverage of the event, we are able to constrain the lens model up to the known ambiguity between close and wide binary lenses. The detection of annual parallax in combination with measurements of extended-source effects allows us to determine the mass, distance and velocity of the lens components for the competing models. While the model involving a close binary lens leads to a Bulge- Disc lens scenario with a lens mass of M = (0.51 ± 0.15) M-&ODOT; and distance of D-L = (2.9 ± 0.4) kpc, the wide binary lens solution requires a rather implausible binary black-hole lens ( M &GSIM; 126 M-&ODOT;). Furthermore we compare current state-of-the-art numerical and empirical models for the surface brightness profile of the source, a G5III Bulge giant. We find that a linear limb-darkening model for the atmosphere of the source star is consistent with the data whereas a PHOENIX atmosphere model assuming LTE and with no free parameter does not match our observations
Y1  - 2005
SN  - 0004-6361
ER  - 
TY  - JOUR
A1  - Beaulieu, Jean-Philippe
A1  - Bennett, David P.
A1  - Fouqué, Pascal
A1  - Williams, Andrew
A1  - Dominik, Martin
A1  - Jorgensen, Uffe Grae
A1  - Kubas, Daniel
A1  - Cassan, Arnaud
A1  - Coutures, Christian
A1  - Greenhill, John
A1  - Hill, Kym
A1  - Menzies, John
A1  - Sackett, Penny D.
A1  - Albrow, Michael D.
A1  - Brillant, Stephane
A1  - Caldwell, John A. R.
A1  - Calitz, Johannes Jacobus
A1  - Cook, Kem H.
A1  - Corrales Cosmeli, Esperanza de Santa Cecilia
A1  - Desort, Morgan
A1  - Dieters, Stefan
A1  - Dominis, Dijana
A1  - Donatowicz, Jadzia
A1  - Hoffman, Martie
A1  - Kane, Stephen R.
A1  - Marquette, Jean-Baptiste
A1  - Martin, Ralph
A1  - Meintjes, Pieter
A1  - Pollard, Karen R.
A1  - Sahu, Kailash C.
A1  - Vinter, Christian
A1  - Wambsganss, Joachim
A1  - Woller, Kristian
A1  - Horne, Keith
A1  - Steele, Iain
A1  - Bramich, Daniel M.
A1  - Burgdorf, Martin
A1  - Snodgrass, Colin
A1  - Bode, Mike
A1  - Udalski, Andr
T1  - Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing
N2  - In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive. Around M-dwarf stars ( the most common stars in our Galaxy), this model favours the formation of Earth-mass (M+) to Neptune-mass planets with orbital radii of 1 to 10 astronomical units (AU), which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars(1-4). More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptune's mass or less have not hitherto been detected at separations of more than 0.15 AU from normal stars. Here we report the discovery of a 5.5(-2.7)(+5.5)M(+) planetary companion at a separation of 2.6(- 0.6)(+1.5) AU from a 0.22(-0.11)(+0.21)M(.) M-dwarf star, where M-. refers to a solar mass. (We propose to name it OGLE- 2005-BLG-390Lb, indicating a planetary mass companion to the lens star of the microlensing event.) The mass is lower than that of GJ876d (ref. 5), although the error bars overlap. Our detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory.
Y1  - 2006
UR  - http://www.nature.com/nature/
U6  - https://doi.org/10.1038/Nature04441
SN  - 0028-0836
ER  - 
TY  - JOUR
A1  - Sanchez, Sebastian F.
A1  - Jahnke, Knud
A1  - Wisotzki, Lutz
A1  - McIntosh, Daniel H.
A1  - Bell, Eric F.
A1  - Barden, Marko
A1  - Beckwith, Steven V. W.
A1  - Borch, Andrea
A1  - Caldwell, John A. R.
A1  - Haussler, Boris
A1  - Jogee, Shardha
A1  - Meisenheimer, Klaus
A1  - Peng, Chen Y.
A1  - Rix, Hans-Walter
A1  - Somerville, Rachel S.
A1  - Wolf, C.
T1  - Colors of active galactic nucleus host galaxies at 0.5 < z < 1.1 from the GEMS survey
N2  - We present the results from a study of the host galaxies of 15 optically selected active galactic nuclei (AGNs) with 0.5<z<1.1 from the Galaxy Evolution from Morphology and SEDs project (GEMS). GEMS is a Hubble Space Telescope imaging survey of a similar to28' x 28' contiguous field centered on the Chandra Deep Field-South in the F606W and F850LP filter bands. It incorporates the spectral energy distributions and redshifts of similar to10,000 objects, obtained by the COMBO-17 project. We have detected the host galaxies of all 15 AGNs in the F850LP band (and 13 of 15 in the F606W band), recovering their fluxes, morphologies, and structural parameters. We find that 80% of the host galaxies have early-type (bulge-dominated) morphologies, while the rest have structures characteristic of late-type (disk-dominated) galaxies. We find that 25% of the early types and 30% of the late types exhibit disturbances consistent with galaxy interactions. The hosts show a wide range of colors, from those of red-sequence galaxies to blue colors consistent with ongoing star formation. Roughly 70% of the morphologically early-type hosts have rest-frame blue colors, a much larger fraction than those typical of nonactive morphologically early-type galaxies in this redshift and luminosity range. Yet, we find that the early-type hosts are structurally similar to red-sequence elliptical galaxies, inasmuch as they follow an absolute magnitude versus half-light size correlation that is consistent with the mean relation for early-type galaxies at similar redshifts
Y1  - 2004
SN  - 0004-637X
ER  -